HEIDENHAIN ND 1300 CNC Setup - Manual (Page 47)

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End positions remain stable?
Integral factors can quickly add up to significant motor drive signals. These signals move the last small
distance to the final target quickly, but might create too much axis motion, causing the axis to move
through the target position. If the axis moves through the target, it must be driven back to the target again
from the other direction, resulting in small axis oscillations around the target position. These oscillations
can be observed in the Current position field as position instability.
Adjust integral and proportional factors
The end position instability described above can usually be eliminated by reducing the integral factor, and
then sometimes increasing the proportional term to stabilize the axis position at the target. If this adjust-
ment is not sufficient to reach the target and stabilize the end position, then it will be necessary to find a
new mixture of proportional, derivative and integral terms, to relax the velocity or increase the continua-
tion zone debounce time.
Set Max Following Error to 2X the amount observed during testing
CNC systems should include primary safeguards such as slip-clutches and limit switches to prevent stage
over-travel and collision damage. The maximum following error term is assigned only as an secondary
safeguard that will halt motion if an obstruction is encountered.
Following errors are shown in the Max following error field during CNC loop tuning and test. The Max
following error assigned in the Max following error field should be about twice the maximum amount
shown during test.
All axes moved together OK?
When the axes are tuned and tested individually, the combination of all axes must be tested simultaneously
to ensure that combined axis CNC performance is satisfactory. This test is performed on the CNC Test
screen.
Readjust faulty axis
If combined axis vibration is observed, identify which axis is at fault, retune that axis, and retest the com-
bined axis CNC movement again. If the problem persists, de-tune an axis (or axes) slightly and test again.
Continue this process until the combined movement of all axes is satisfactory.
CNC Setup and PID Loop Tuning Guide